Optical Sensor Charge Package Segmentation for Precision
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Solution Overview
Problem
The accuracy of light-to-frequency conversion in optical sensor arrangements is limited by the size of well-defined charge packages used in integration, particularly in low light conditions where smaller charge packages are not well-defined over temperature and process variations.
Innovation Solution
The implementation of a calibration phase to determine the relationship between well-defined and not well-defined charge packages, allowing for the use of smaller charge packages in residual measurement phases to improve accuracy, and the introduction of an ON-OFF-compensation phase to account for switching effects, along with leakage current measurement to correct for internal errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If well-defined charge packages are used for integration, then reliability is improved, but measurement precision deteriorates due to the limited accuracy from larger charge package size
Solution Approach 1:
The integration process is segmented into two distinct phases: a first integration phase using well-defined charge packages for reliable counting, and a second integration phase using smaller, less well-defined charge packages for higher precision residual measurement. This segmentation allows each phase to use charge packages optimized for its specific purpose.
Solution Approach 2:
The first integration phase using well-defined charge packages is performed as a preliminary action before the second integration phase. This preliminary integration establishes a stable baseline that enables subsequent high-precision residual measurement with smaller charge packages.
2Measurement precision
If smaller charge packages are used for integration, then measurement precision is improved, but reliability deteriorates due to poor definition over temperature and process variations
Solution Approach 1:
The integration process is segmented into two distinct phases: a first integration phase using well-defined charge packages for reliable counting, and a second integration phase using smaller, less well-defined charge packages for higher precision residual measurement. This segmentation allows each phase to use charge packages optimized for its specific purpose.
Solution Approach 2:
The second integration phase uses only a partial amount of charge (smaller charge packages) to measure the residual integration value. This partial action with smaller charge packages provides the necessary precision for the residual measurement without requiring the full stability of well-defined charge packages.
3Measurement precision
If calibration phase is added to determine relationship between charge packages, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The calibration phase is performed as a preliminary action to determine the relationship between the first and second charge packages. This calibration data is stored and used during subsequent measurement phases, enabling high precision without adding complexity to the ongoing measurement process.
Solution Approach 2:
The calibration phase provides feedback information (the relationship between charge packages) that is used to correct and refine the integration values in subsequent phases. This feedback mechanism enables precision improvement without requiring continuous complex operations.
4Measurement precision
If photodiode is disconnected during calibration phase, then measurement precision is improved by avoiding photocurrent influence, but loss of time occurs due to switching operations
Solution Approach 1:
The photodiode disconnection during calibration is a preliminary action performed once before actual measurements. This one-time switching operation establishes accurate reference data that enables precise measurements during subsequent phases without requiring repeated switching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of light sensing by improving the integration value precision to the size of smaller charge packages, enabling more accurate ALS measurements even under low light conditions, such as those encountered in mobile phone displays.
Implementation Method 1
an optical sensor arrangement often comprises a photodiode as a light detector and measures a photocurrent flowing through the photodiode
Data Source
AI summary
An optical sensor arrangement has an integrator, a photodiode for providing a current corresponding to a first polarity, a comparator coupled to the integrator for comparing a voltage with a threshold voltage to provide a comparison output, a reference charge circuit and a control unit. The reference charge circuit is coupled to the integrator for selectively providing first charge packages of a first size or second charge packages of a second size. The control unit is configured to control operation in a calibration phase, in an integration phase and in a residual measurement phase. During the calibration phase, the reference charge circuit provides one of the first charge packages and one or more of the second charge packages to the integrator until the comparison output changes. A reference number is determined corresponding to a number of the second charge packages provided. During the integration phase, the photodiode is connected to the integrator and the reference charge circuit provides one of the first charge packages to the integrator in response to a respective change of the comparison output. An integration number corresponding to a number of the changes of the comparison output is determined. During the residual measurement phase that immediately follows the integration phase, the reference charge circuit provides one or more of the second charge packages to the integrator until the comparison output changes. A residual number corresponding to a number of the second charge packages provided is determined.